bias port?

ian33 · 16th May 2011, 01:51 AM

What test can be done with a DVM to determine if the bias port in the output section of an amp is where it suposed to be?

Perry Babin · 16th May 2011, 03:36 AM

What amp?

ian33 · 16th May 2011, 07:28 PM

Sometimes i get amplifers other tech has tried to repair an maybe change the bias settings.so i just want to no how to go about finding where it suposed to be.

Perry Babin · 16th May 2011, 07:51 PM

If the manufacturer has specific settings, use those. For generic amps where there is no information available for bias settings, I use the amp meter on the 12v power supply.

Set the bias at the full minimum. Rotate the pot slowly until the amp meter just barely begins to move. That indicates that the outputs are biased slightly on. If you're not familiar with the amp, you should runt it up to near thermal to confirm that the bias/idle current doesn't increase significantly at high temperatures. The following demo shows the basic procedure.
http://www.bcae1.com/temp/ausettingbias.swf

16th May 2011, 01:51 AM	#1
ian33 diyAudio Member Join Date: Jun 2010 Location: the caribbean	bias port? What test can be done with a DVM to determine if the bias port in the output section of an amp is where it suposed to be?

16th May 2011, 03:36 AM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	What amp? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

16th May 2011, 07:51 PM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	If the manufacturer has specific settings, use those. For generic amps where there is no information available for bias settings, I use the amp meter on the 12v power supply. Set the bias at the full minimum. Rotate the pot slowly until the amp meter just barely begins to move. That indicates that the outputs are biased slightly on. If you're not familiar with the amp, you should runt it up to near thermal to confirm that the bias/idle current doesn't increase significantly at high temperatures. The following demo shows the basic procedure. http://www.bcae1.com/temp/ausettingbias.swf __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

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16th May 2011, 07:28 PM	#3
ian33 diyAudio Member Join Date: Jun 2010 Location: the caribbean	Sometimes i get amplifers other tech has tried to repair an maybe change the bias settings.so i just want to no how to go about finding where it suposed to be.

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